Such "sonic boom clouds" can occur when aircraft fly fast enough to cool the air around them, causing moisture in the air to condense. Shortly after launch, the Ares I-X rocket was traveling at more than four times the speed of sound.

The rocket's six-minute, U.S. $450-million flight was designed to help NASA refine its plans for Ares I, the next-generation craft that--combined with the Orion crew capsule--is slated to replace the aging space shuttle as the U.S.'s primary means of ferrying humans and cargo into space.